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Indicator locks, particularly having non-numeric indicators, broadly define the art wherein the present invention resides. Lock engagementxe2x80x94has the latch and/or dead bolt been thrown?xe2x80x94or else room occupancyxe2x80x94did somebody now inside this room lock this lock?xe2x80x94are commonly indicated conditions. Left unaddressed by the prior art of which applicant is aware is a different, and essentially evidentiary, question. Given the desirability of permitting a known party to enter a lock-protected space ad hoc or on schedule (a landlord in an emergency, a house sitter to feed cats, etc.), how should a lock best indicate that such an event has occurred, while preserving its operability for all of the parties having keys, meanwhile providing the lock owner with the option of presenting evidence of, and/or of confronting with evidence of, entry improperly sought or gained, or of a trust neglected?
Cylindrical elements that are geared or journaled to rise up or are pushed by a spring-loaded lever into full extension are well-known as indicator devices. Parts for lock mechanisms, including such button-form indicators, generally are made from cast metal and/or from sintered, powdered metal, and springs of all sorts find lock-mechanism application. For short, cylindrical parts a half-inch in diameter, tolerances of xc2x10.3% or better are economically and routinely achieved using powdered-metal injection molding. Tight tolerances make possible functional refinement.
The principal objective of the present invention is to answer, then, by means of an exemplary, high-precision lock producible with advanced but available technology, the evidentiary question articulated above.
U.S. Pat. No. 1,177,151 to Teich (1916) discloses a lock indicating mechanism having a button-type indicator driven by a spring always into the lock (p. 3, lines 82-84), not outwardly as in the present invention. Teich""s indicator furthermore requires the movement of a bolt, this movement having the effect of deadlocking the door to which the lock is applied, for the shank of Teich""s indicator to become visible. In the present invention, merely the slight rotation of a key in the lock, occurring well before any bolt is thrown, is all that is required for that key""s associated indicator to pop out. Teich""s motivation, described on p. 3, lines 101-116, is to prevent an occupied room from being disturbed. The present invention""s motivation is broader and has to do with trust not being misplaced or abused.
U.S. Pat. Nos. 1,154,142 and 1,177,152 to Teich (1915, 1916) disclose three classes of keys. These keys, however, are hierarchical, in that the operation of Teich""s lock by at least one of the keys excludes operation of the lock by the remaining key or keys (U.S. Pat. No. 1,154,142 p. 1, lines 18-21; and 1,177,152 p. 1, lines 16-19). In the present invention all of the keys are equal with respect to operation of the lock qua lock. No key excludes any other key.
U.S. Pat. No. 2,638,770 to Gutman (1953) discloses a lock-indicating mechanism having a button-type indicator driven by a spring into the lock (FIG. 7 and col. 3, lines 71 to col. 4, in 1), not outwardly as in the present invention. Gutman""s indicator is furthermore designed to indicate whether a dead bolt has been thrown from inside or from outside a room, and is operable exclusively by the retractors that operate the lock""s dead bolt. Both the mechanism as well as motivation of Gutman""s indicator are entirely different from the present invention""s.
U.S. Pat. No. 3,336,775 to Russell et al. (1967) shows a button-type indicator driven by a spring into the lock (FIG. 5 and col. 3, lines 34-38). Furthermore, xe2x80x9cthe position of the indicator member is directly related to the position of [the lock""s] dead boltxe2x80x9d [col. 4, lines 37-38]. The mechanism and motivation of this indicator lock are entirely different from the present invention""s.
U.S. Pat. No. 526,740 to Rapaport (1894) appears at first glance to have an indicator means, xe2x80x9cdog 28xe2x80x9d, that is urged out of Rapaport""s combination lock. On reading, however, we discover that xe2x80x9cdog 28xe2x80x9d is not an indicator means at all but is rather a counting means (page 2, lines 77-80). In fact, xe2x80x9cdog 28xe2x80x9d indicates nothing whatever about the present condition of Rapaport""s lock nor about its use by parties with knowledge of its combination.
U.S. Pat 2,793,522 to Tornoe (1957) discloses a geared indicator able to show only whether the lock is locked or not. The mechanism and motivation of Tornoe""s lock differ entirely from the present invention""s. Interesting in Tornoe is FIG. 2, because this figure is what a linguist might term a near homograph of the present invention. What the unnumbered circle to the right of tumbler 18 in Tornoe""s FIG. 2 might be, Tornoe never says, even though this detail appears again in mirror image in FIGS. 3 and 4, and appears slightly extended in FIG. 5 (n.b. 37 refers to the lock face). Homographs like homonyms, however, have totally different meanings.
U.S. Pat. No. 3,885,409 to Genakis (1975) shows a cylinder lock having xe2x80x9ca set of independently rotational rings on the plug, one ring for each pinwayxe2x80x9d [col 2, lines 48-50]. Genakis then adds further rings, but is motivated exclusively by two desires: to increase the number of lock combinations and to make the lock more difficult to pick. Genakis gives no shape to his rings that might enable them to serve in additional, functional capacities.
The present invention confines cylindrical indicators, the xe2x80x9cpop-upsxe2x80x9d, in cylindrical bores parallel to and close to the lock""s rotatable core. The pop-ups are urged forward from behind by springs but are prevented from movement by pins which drop into bores orthogonal to the pop-up""s length. The pop-ups are now armed. Ring-like elements are mounted over the lock-core that are so formed as to be able, on rotation with the core by a key, to lift these obstructing pins and thus to release the po-pup to pop up. Stops prevent the pop-ups from shooting out of the lock. In the instant before a stop is encountered, a pin falls from above into a bore in the pop-up placed orthogonal to its direction of motion, thus locking the pop-up, so that it cannot be pressed back in. A different key, which cannot trigger a po-pup, has the ability, via a different, core-mounted ring, to lift this locking pin, so that the pop-up may be reset. In the preferred embodiment, two independent pop-ups are provided. The pop-ups"" armed positions may be symbolically indicated in a variety of ways, as for example by the letters A and B (alternatively by such non-lingual symbols as xe2x96xa1 and ◯), with the pop-ups"" respective xe2x80x9cpopped-outxe2x80x9d, or indicator, positions being indicated symbolically by AA and BB (alternatively by ▪ and xe2x97xaf) Having two pop-ups entails locating the lock""s tumblers asymmetrically in the plane containing their axes. This is unusual and enhances considerably the security of the lock against anyone not thoroughly familiar with its construction and not equipped with the necessary, proprietary lock picks.
The present invention has several important objects, among which are:
1) security against unannounced entry by persons having contractually-guaranteed access to a key
2) security against an intruder who has somehow gained access to a key
3) security against curiosity snooping
4) enhanced ability to monitor the performance of an employee
5) enhanced security through keys having asymmetrically placed keycuts
6) enhanced security through keys having independent, dummy keycuts